Free Classifieds Websites

Hi,

I hope this is the right place to post this.
I already have a steadily growing free local classifieds site.
There are so many free classified sites on the net. Both local and global ones. Apart from the super popular ones (like Craiglist, Backpage) there are sites that get hundred thousands of visitors.

For eg:
USA: classifiedads.com, oodle.com, yakaz.com, recycler.com, geebo.com
UK: gumtree.com; pistonheads.com; vivastreet.co.uk; freeads.co.uk; loot.com
India: quikr.com; click.in; indialist.com; khojle.in, magicbricks.com

All of them provide the same service. Site functions, how they work, they are almost same.

So my question is how did they get to be so popular when they provide same service? Lets take India for eg, above mentioned Indian sites may not be "equally" popular but they still get huge amount of visitors judging by the alexa rank.

Was it their advertising?
Did they get any funding?
Am I missing some unique feature on each of those sites?

Is there anyone who can shed some light on this?

Thanks